Comparative Study of The Effects of Confounding Factors on Improving Rat Pancreatic Islet Isolation Yield and Quality

OBJECTIVE

Isolated pancreatic islets are valuable resources for a wide range of research, including cell replacement studies and cell-based platforms for diabetes drug discovery and disease modeling. Islet isolation is a complex and stepwise procedure aiming to obtain pure, viable, and functional islets for in vitro and in vivo studies. It should be noted that differences in rodent strains, gender, weight, and density gradients may affect the isolated islet's properties. We evaluated the variables affecting the rat islet isolation procedure to reach the maximum islet yield and functionality, which would be critical for further studies on islet regenerative biology.

MATERIALS AND METHODS

The present experimental study compared the yield and purity of isolated islets from nondiabetic rats of two different strains. Next, islet particle number (IPN) and islet equivalent (IEQ) were compared between males and females, and the weight range that yields the highest number of islets was investigated. Moreover, the influence of three different density gradients, namely Histopaque, Pancoll, and Lymphodex, on final isolated islets purity and yield were assessed. Finally, the viability and functionality of isolated islets were measured.

RESULTS

The IEQ, IPN, and purity of isolated islets in 15 Lister hooded rats (LHRs) were significantly (P≤0.05) higher than those of the other strains. Male LHRs resulted in significantly higher IEQ compared to females (P≤0.05). Moreover, IPN and IEQ did not significantly vary among different weight groups. Also, the utilization of Histopaque and Pancoll leads to higher yield and purity. In vivo assessments of the isolated islets presented significantly reduced blood glucose percentage in the transplanted group on days 2-5 following transplantation.

CONCLUSION

Based on these results, an optimal protocol for isolating high-quality rat islets with a constant yield, purity, and function has been established as an essential platform for developing diabetes research.

Autophagy Involves in Differentiation of Insulin-Secreting Cells from Adipose Derived Stem Cells

OBJECTIVE

Destruction of pancreatic beta-cells induces an insulin deficiency and causes type 1 diabetes. The role of autophagy in inducing insulin-secreting cells (ISCs) from adipose-derived mesenchymal stem cells (AMSCs) was investigated in the current study.

MATERIALS AND METHODS

In this experimental study, the isolated AMSCs were characterization and exposed to a cocktail differentiation medium (CDM) in the absence or presence of 3-methyladenine (3MA), an autophagy inhibitor. The differentiation of ISCs was confirmed by the evaluation of the expression of beta-cell-specific genes including pancreatic and duodenal homeobox 1 (PDX1), musculoaponeurotic fibrosarcoma oncogene homolog A (MAF-A), Nk class of homeodomain-encoding genes 6.1 and 2.2 (NKX6-1 and NKX2.2), Glucose transporter 2 (GLUT-2) and INSLIN. Using Newport Green (NG), insulin-positive cells were identified. Insulin secretion in response to various glucose concentrations was measured. Autophagy was evaluated by Acridine orange (AO) staining. Also, expression of autophagy-associated genes, including autophagy-related gene 5 (ATG-5), autophagy-related gene 7 (ATG-7), BECLIN-1, and mammalian target of rapamycin (mTOR), was evaluated by Real-time polymerase chain reaction (PCR) method.

RESULTS

We observed a significant increase of beta-cell specific genes expression in the CDM-treated cells (P<0.01 or P<0.001), whereas the expression of these genes was down-regulated in 3MA-exposed cells. Expression of INSULIN and GLUT-2 genes (P<0.01 and P<0.05, respectively), insulin secretion in response to glucose (P<0.01), and percentage of NG-positive cells (P<0.05) in the 3MA-exposed cells were considerably lower than the cells treated with CDM. The percentage of AO-positive cells (P<0.01) and the expression of autophagy-related genes (P<0.001) was significantly enhanced in the CDM group. These events were significantly prevented by the 3MA.

CONCLUSION

Our data showed that autophagy is necessary for beta-cell differentiation, and preventing autophagy by 3MA causes the reduction of beta-cell differentiation and insulin secretion.

In Vitro Differentiation of Human Umbilical Cord Blood CD133(+)Cells into Insulin Producing Cells in Co-Culture with Rat Pancreatic Mesenchymal Stem Cells

Objective

Pancreatic stroma plays an important role in the induction of pancreatic cells by the use of close range signaling. In this respect, we presume that pancreatic mesenchymal cells (PMCs) as a fundamental factor of the stromal niche may have an effective role in differentiation of umbilical cord blood cluster of differentiation 133⁺ (UCB-CD133⁺) cells into newly-formed β-cells in vitro.

Materials and Methods

This study is an experimental research. The UCB-CD133⁺cells were purified by magnetic activated cell sorting (MACS) and differentiated into insulin producing cells (IPCs) in co-culture, both directly and indirectly with rat PMCs. Immunocytochemistry and enzyme linked immune sorbent assay (ELISA) were used to determine expression and production of insulin and C-peptide at the protein level.

Results

Our results demonstrated that UCB-CD133⁺differentiated into IPCs. Cells in islet-like clusters with (out) co-cultured with rat pancreatic stromal cells produced insulin and C-peptide and released them into the culture medium at the end of the induction protocol. However they did not respond well to glucose challenges.

Conclusion

Rat PMCs possibly affect differentiation of UCB-CD133⁺cells into IPCs by increasing the number of immature β-cells.